[mothered]

When first applied nothing just printed on the water solulable paper looks exactly same as normal paper

Sounds good.

The time for the ice to melt through to dissolve the paper would be a few hours maximum then the label would be gone 

This could be a problem for shipments with a greater storage time.

If the label disappears while the package Is still at the depot awaiting delivery allocation, It may be Identified against the details recorded on the manifest.